Cooling unit for refrigeration apparatus



Dec. 2, 1952 w. G. KOGEL 2, 9, 0

COOLING'UNIT FOR REFRIGERATION APPARATUS Filed Feb. :5, 1948 4 Sheets-Sheet 1 Dec. 2, 1952 w; G. KOG EL 2,619,805

, COOLING UNIT FoR REFRIGERATION APPARATUS Filed Feb. 3, 1948 4 Sheets-Sheet 2 I A- i W" E '4; 5 i 36- 4 5 3'5 Dec. 2,1952 w. G. KOGEL COOLING UNIT FOR REFRIGERATION APPARATUS Filed Feb. 3, 1948 4 Sheets-Sheet 3 Ell Tu E

v, M W 7 Dec- 2; 1952 w. G. KOGEL COOLING UNIT. FOR REFRIGERATION APPARATUS F il ed Feb. :5. 19 48 4 Sheets-Sheet 4 INSULATION IN V EN TOR. 24 W Patented Dec. 2, 1952 UNITED STATES PATENT orrioe COOLING UNIT FOR REFRIGERATION v APPARATUS Wilhelm Georg Kiigel, Stockholm, Sweden, as-

signor to Aktiebolaget Elektrolux, Stockholm, Sweden, a corporation of Sweden Application February 3, 1948, Serial No. 6,062 In Sweden February 4, 1947 My invention relates to refrigeration, and more particularly to evaporators or cooling units for refrigeration apparatus.

In refrigerators of the household type having a thermally insulated storage space, the evaporator or cooling unit is arranged to provide refrigeration both for making ice cubes and storing frozen food packages and other matter to be frozen, and also for maintaining the air in the space at a desired low temperature for properly preserving foods. It is often the practice to provide evaporators or cooling units which wil1 effectively conduct heat from trays adapted to contain water to be frozen and will also present an extensive heat transfer surface for cooling air flowing in contact therewith.

practice to make use of the walls of the casing or housing to provide a relatively extensive heat transfer surface for cooling air flowing in contact therewith. In evaporators or cooling units of this kind the Walls of the housing are generally at a temperature which is below the dew point of air and objectionable condensation of moisture takes place at the walls.

Further, in absorption refrigeration apparatus it is customary for the cooling unit to be inserted into and removed from a storage space through an opening in a thermally insulated wall thereof which is adapted to be closed by a closure member. Heretofore it has usually been the practice to mount the casing o-r shell in thermal exchange relation with the evaporator coil before the cooling unit is inserted into the storage space, thereby necessitating an opening of adequate size to accommodate the shell or casing. This is objectionable because it is desirable to keep the opening in the thermally insulated wall of minimum size in order to reduce the tendency for heat transfer into the storage space at the closure member employed to close the wall opening.

It is an object of my invention to provide an evaporator or cool ng unit having a casing or housing whose walls are maintained substantially free of condensed moisture and which will be highly effective to make ice cubes and store frozen food packages and other matter to be frozen and also present an efficient heat transfer surface" for cooling air flowing in contact therewith. I accomplish this by providing a housing 8 Claims. (Cl. 62-403) 2 having a supporting surface for ice trays or the like which is in good thermal relation with a refrigerant passage while the exterior surfaces of the walls of the housing are thermally shielded from the refrigerant passage in such manner that the exterior surfaces will be maintained above the condensation temperature of moisture or water vapor present in air circulating in the storage space under stabilized temperature conditions therein. More particularly, I provide a, supporting surface for ice trays or the like which is in good heat conducting relation with a looped coil forming a refrigerant passage and a housing for such supporting surface and looped coil which 1 is in poor' heat conducting relation therewith, the housing having openings for circulation of air therethrough to bring air in thermal transfer relation with the refrigerant passage. The refrigerant passage desirably ineludes one portion adapted to operate at a low temperature which is arranged in heat conducting relation with the supporting surface, and another portion adapted to operate at a higher temperature which presents an extensive heat transfer surface for cooling air circulating through the housing and coming in contact therewith.

The housing is advantageously employed to collect moisture produced therein due to cooling of air flowing in thermal relation with the refrigerant passage, and one of the openings-in the housing through which air passes may also serve as a drain for collected moisture. Further, the opening in a thermally insulated wall of a storage space may be of minimum size to permit inserting the looped coil into the space,v and the housing may thereafter be mounted in position on the coil through the front access opening of the space.

The invention, together with the above and other objects and advantages thereof, will be better understood from the following description taken in conjunction with the accompanying drawings forming a part of this specification, and of which:

Fig. 1 illustrates more or less diagrammatically absorption refrigeration apparatus of the inert gas type having an evaporator formed of piping which may be employed to provide a cooling unit embodying the invention;

Fig. 2 is a fragmentary side vertical sectional view of a, refrigerator illustrating a cooling unit embodying the invention which includes an evaporator formed of piping and generally like that schematically shown in Fig. 1; v

Fig. 3 is a perspective view of the housing or view similar to Fig. 2 illustrating anotherem bodiment of the invention;

Fig. 7 is a front sectional View taken at line 1-1 of Fig. 6;

Fig. 8 is a fragmentary sectional view illustrating a further embodiment of'the invention; and

Fig. 9 is a perspective view of partsembodied in the cooling unit shown in Figs. 2 .to .inelusive.

Evaporators of absorption refrigeration apparatus of a-uniform pressure type, which are "formed of piping, are advantageously employed to provide cooling units embodying the invention. Such absorption refrigeration apparatus,

inwhich an inert gas or pressure equalizing fluid is employed, is diagrammatically shown in Fig. 1. In refrigeration apparatus of this type refrigerant'fiuid, such as liquid ammonia,.for example, is i-ntrod'uced' through a conduit t into the'evaporator I I rates and diffuses in the evaporator ll into an inert gas, such as hydrogen, for example, to produce refrigeration and abstract heat-from the surroundings.

The resulting gas mixture of refrigerant and inert gas flows from the evaporator through an outer passage of a gas heat exchanger l2 and vertical conduit l3 into an absorber comprising a vessel 14 and a looped coil l5. In the absorber vessel 14 and coil l5 the refrigerant vapor is absorbedby a suitable absorbent, such as water,

for example, which is introduced into coil it through a condiut 16. The hydrogen 101' :inert gas, which is practically insoluble and weak in refrigerant, returns to'theevaporator l I from coil '85 'through an inner passage of the gas :heat exchanger l2 and a conduit [1.

From the vessel I' l enriched absorption liquid flowsthrough a conduit 1'8 and inner'passage "o'f a'liquid heat exchanger 19 into the lower end of a vapor lift tube 20 of a generator or vapor expulsion unit 21. The .generator'unit 21 comprises a heating .flue '22 having the vapor lift tube 2i] anda boiler pip'e' 23'inithermal'exchange relation therewith, as :by welding, .for example.

iBy .h'eatin'g generator unit .2] as 'by' agas burner 24, for example,.liquid from the inner-passage of the 'heatiexchanger :IB is raised by vapor lift action through tube 28 into the upper part of the boiler pipe23. The liberated refrigerant vapor entering boiler "pipe 23 from the tube 125,

and also vapor expelled :from solution in the boiler'pipe, flows upwardly into an air cooled from boiler pipe 23 througha conduit 21, .outer "passage of the liquid heat exchanger 1.9 and conduit-l6 into the upper v.part of the coil I5. The lower end of the condenser25 is connected by a conduit 28 to the gas circuit, as .to .the

upper -;part\of absorber coil 15,..for example, so

The refrigerant fluid evapoin a single substantially ,horizontalplane.

'4 that any non-condensable gas which may pass into the condenser can flow to the gas circuit and not be trapped in the condenser.

The evaporator ll includes upper and lower portions Na and llbwhich are connected in series relation with inert gas from conduit I'I flowing upwardly through the upper portion I la in the presence of and in counterflow to liquid .refrigerant which is introduced through conduit .1 0. Unevaporated liquid refrigerant is conducted from the lower part of the upper portion Ila through :a conduit '29 from which liquid refrigerant passes into the lower portion lib for downward flowin the latter in the presence of .and in parallelfiow with the inert gas.

--Since the inert gas flows successively through the evaporator portions lid and Nb, the gas in the upper portion lla contains a lesser amount of refrigerant vapor than the gas in the lower portion i lb. The partial vapor pressure of the refrigerant is a gradient, so that the temperature of the liquid refrigerant inthe evaporatoriportions is also a gradient, the average or mean evaporating temperature of the liquid being lower in the upper portion I la which constitutes the freezing section of the evaporator.

In Fig. 2 I- have shown an evaporator i I" formed of piping and generally like that just described arranged in a thermally insulated storage space 3D-of a household refrigerator 3! havinga-front accessopening 32 adapted to be closed by-a .door

(not shown) hinged to the front {of the refrigerator cabinet. As best shownin Figs. 2, 3 and 4, the evaporator portions Ha and llb are in the form of looped coils .each of which is positioned In order to position the evaporator H in the storage space 38, the rearwall v33 thereof is formed with anopeningtd defined by a rectangular frame-35 which may be formed .of wood, for example. The openingfi tis arranged to be closed by a cover or closure member .35 whichbears against a gasket Blof suitable ,insulatingmaterial and. is .removably. secured at .36 to the rear wall 33. Thecover 3.6 contains asuitable insulating material .and parts .of .the refrigeration apparatus extend .therethrough which connect the evaporator l I with other parts disposedexteriorly of the storagespace 33.

In Figs. 2, 4 and 5, parts of the evaporator ll similar to those diagrammatically illustrated in Fig. 1 are referred to by the samereference numerals. As best seen in Fig. ,4 liquid refrigerant is introducedinto the upper evaporator portion Ila through conduit 18 and flows therethroughin counteriiow to inert gas which enters this upper evaporator portion through conduit I] whose lower endisconnected to the gas heat exchanger [2. Inert gas passes .fromthe upper evaporator portion i la through a connection 39 into the lower evaporator portion [lb and flows therethrough inparallel flow with liquid refrigerant. whichenters this portion through the conduit 29. The conduits Ill and 2,9,may. be arranged in heat exchange relation, as best seen in Figs. 1 and 5.

From the lower-evaporator portion. I lb the rich .mixture of. inert gas and refrigerant vapor flows through a conduit .48 which is connected to the outer passage. of the gas heat exchanger in the manner shown in Fig. .1. The/conduit I! through which inert .gas passes to the upper evaporator portion Ila is formed witha U-shaped bend, as indicated at 4| in Fig. 4. In order to prevent any liquid accumulating in theibendll, a lJ-trap-AZ is connected thereto and to the conduit where'- by such liquid can freely drain by gravity flow into the gas heat exchanger 12 and pass downwardly to the absorber vessel.

In accordance with my invention the evaporator ll forms part of a cooling unit 44 comprising a casing 45 having a shelf 46 therein. The shelf 46 is formed from a substantially flat plate member having bent sides or edges 4'! which snugly receive the outermost straight sections of the upper evaporator coil portion i la. An inverted U-shaped member 48, which is fixed to the underside of the' supporting surface, is provided with flanges 49 to form grooves which receive inner straight sections of the upper evaporator coil portion Ha. Before the evaporator H is positioned in the storage space 36 the shelf 46, member 48 and upper evaporator coil portion I la may be dipped into a body of molten zinc or provided with a suitable corrosion protecting agent in any other manner. In this way the parts are protect ed against corrosion and a good heat conducting path is provided between the shelf 46 and looped coil for abstracting heat from matter placed on the shelf.

6 While the shelf 46 is in good thermal relation with the upper looped coil portion I la, the casing 45 is arranged in such manner that it is thermally shielded from and in poor heat conducting relation with respect to the looped coil portion Ha. In the embodiment of Figs. 2 to 5 inclusive, this is accomplished by securing guides or rails 50 to the sides of the shelf 46, as by welding or brazing, for example. The guides or rails 50 receive and support L-shaped tabs or hooks 5i fixed to the inside surfaces of the sidewalls of the casing 45. The guides 56 are of such shape that they form open-ended grooves which snugly receive the hooks 5| when the casing 45 is moved rearwardly on the guides from the front access opening 32.

Since the casing 45 is only supported on the upper coil evaporator portion Ila at the regions of the relatively small hooks or tabs 5| and the casing otherwise is in spaced relation with respect to the shelf 46 and upper evaporator portion, an extremely poor heat conducting path is provided between the casing and evaporator parts upon which it is supported. This heat conducting path is of such small magnitude that for practical purposes it may be stated that thecasing 45 is. outof thermal contact with the upper coil evaporator portion Ha.

When the housing 45 is slidably moved into position on the guides 56,"an opening 52 at the front thereof 'islocated above the shelf 46 through whichice trays and other matter to be frozen can be inserted into and withdrawn from the upper freezing compartment 53 of the cooling unit 44. A cover (not shown) is desirably hinged to the front of casing 45 for closing the opening 52 and may be suitably spring-biased to its closed posiutilized to cool air flowing in contact therewith.

Air cooled by thermal transfer with the lower evaporator portion 1 lb passes through the opening 56 and flows downwardly in the storage space 30, thus displacing warmer air which, flows upwardly and passes through the opening 55 into the compartment 54. Such natural circulation of air is indicated by the arrows in Figs. 1 and 3 and is promoted by the difference in specific weights of air at different temperatures.

Water vapor present in air flowing in thermal transfer with the evaporator portion Ilb is condensed on the surfaces of this evaporator portion, and the moisture or condensate removed from air in this manner falls by gravity into the bottom of the casing or housing 45. Hence, the casing 45 is advantageously employed to collect condensed water vapor, and the bottom thereof may slope downwardly toward the opening 56 which may be utilized as a condensate drain. A suitable vessel to receive condensate may be positioned below the opening 56 at such a level that it will not interfere with the natural circulation of air through the bottom compartment 54.

By employing the guides or rails 50 at the sides of the shelf 46 and utilizing relatively small hooks or tabs 51 to support the casing 45 in position on the rails, as just described, it is possible to provide an arrangement whereby the exterior surfaces of the casing will be maintained at a temperature above the dew point of air in the storage space 3!! under substantially stabilized temperature conditions therein, that is, under operating conditions which may be referred to as stationary conditions after normal operation of the refrigerator for an interval of time. By maintaining the exterior surfaces of the casing 45 at a temperature which is always above the freezing temperature of water vapor present in the air and at a temperature at which for the most part Such water vapor will not condense thereon, such exterior surfaces will be substantially free of moisture, thus avoiding dripping of moisture onto food products stored beneath the casing and providing a cooling unit which is easily kept clean and tidy.

In the event some moisture occasionally should precipitate on the casing 45 at the exterior surface thereof, such moisture is readily absorbed by air flowing in contact therewith inasmuch as the casing is considerably warmer than. the evaporator portions Ha and HI) and shelf 45 thermally connected to the evaporator portion I I a. Such absorbed moisture is subsequently condensed out of air when circulating through the interior of the casing 45 in thermal transfer with the lower evaporator portion llb, the path of flow of air circulating through the casing being defined at least in part by the inner faces of the vertical side walls and bottom horizontal wall of the easing.

The casing 45 may be formed of suitable sheet metal provided with an enamel coating atthe exterior surface thereof which is readily kept clean. The exterior surface of the casing when formed of sheet metal may also be provided with a layer or coating of material having poor thermal conductivity, such as artificial resinous substances, for example, or the casing in its entirety may be formed of suitable material possessing poor thermal conducting properties.

The cooling unit of the invention is especially suitable for use with evaporators of absorption refrigeration of the type illustrated in Fig. l and described above, because an opening of minimum size need only be provided in a thermally insulated wall of the storage space to position the looped evaporator coil therein. After the looped evaporator coil is positioned in the storage space,

the casing or housing of the cooling unit canbe readily: mounted on therev-aporator coil in'the mann'er'previously described. The casing 45 is supported in its entirety by the upper eva orator coil portion Ila and not only is substantially out of thermal contact therewith for all practical purposes, as previously explained, but is also in spaced relation with respect to the lower evaporato'r'portion III).

In" Figs. 6and 7 I have shown another embodiment'of the invention in which the upper and lower cooling elements Ila and Ho are disposed within a container or shell 55' which extends from one side Wall 58 to the opposite side wall of the refrigerator cabinet and serves as a partition which dividesthestorage space into top and bottom compartments 59 and 69, respectively.

In the embodiment of'Figs. 6' and '7, the shell or container 55 is fixed to the closure member 36 which is generally like the closure member 36 in Fig. 4 and differs therefrom in that it bears against agasket 3'! located at the inner liner 6! and is removably secured at 38' to the rear wall of the cabinet. The evaporator coil portions Ha and llb are connected to other parts of the refrigeration apparatus generally in the same manner as the evaporator portions Ho and llb, as described above.

The low temperature evaporator portion lid is in thermal contact with the underside of the top 62 of the container 45 and is primarily effective to abstract heat from the upper compart ment 59 which constitutes the freezing section of the refrigerator. Such freezing section desirably is provided with a closure member (not shown) at its front access opening to keep matter stored therein at the lowest possible temperature.

A partition 6-3 may be provided within the container 45 at a level below the upper evaporator portion I la and above the lower evaporator portion. Such partition may be formed of material having poor heat conducting properties and thermally shields the upper and lower evaporator portions from one another.

The container 45 is formed with openings 55 and 56 for circulating air in the bottom compartment 69 in heat transfer with the higher temperature evaporator portion llb. Hence, cooling of air is effected in Figs. 6 and 'Z by the evaporator coil portion i lb in the same manner previously explained above in connection with the first described embodiment.

The container 35 is desirably formed of sheet metal whereby a good heat conductive path is provided for abstracting heat through the top 62 upon which ice trays and other matter to be frozen are placed. However, the remaining walls of the container are provided with an outer layer 85 of suitable insulating material, as best shown in Fig. '7. In this manner the exterior surfaces of the container 45' which are contacted by air circulating in the bottom compartment 66 will be effectively maintained at a temperature above the dew point'of the air and will remain substantially free of moisture.

In Fig. 8 I have shown a further embodiment which may be employed in place of the guides or rails 5% and cooperating hooks or tabs 5| in the first described embodiment for mounting the shell 45 on the upper evaporator portion lla. In Fig. 8 small blocks 66 formed of suitable insulating material, such as Bakelite, for example, may be fixed at El to the side edges of the shelf 46".

In mounting the shell 45 in position the latter is slipped over the upper and lower evaporator portions, as in the firstdescribed embodiment.

The side walls of the shell fit snugly, against the insulating blocks 66 and may be detachably-secured thereto, as indicated at B3. In the arrange ment provided in Fig. 8, two relatively small insulating blocks 66 may be employed at spaced apart regions at each side of the shelf 46 so that the casing 45" Will be substantially out'of thermal contact with the shelf and upper evaporator portion lla connected thereto. In this way the walls of the casing can be eifectively maintained at a temperature above the condemsation temperature of water vapor present in air circulating in the storage space.

Modifications of the embodiments of my invention which I have described will occur to those skilled-in the art, so that I desire'my invention not to be limited to the-particular arrangements set forth and intend in the claims to cover all modifications which do not depart from'thespirit and scope of the invention.

What is claimed is: g

1. A cooling element comprising a firstcoil adapted to be operated at a low average or mean temperature and a second coil below said first coil adapted to be operated at a higher average or mean temperature, a, horizontally disposed member in good heat conducting relation'with said first coil for supporting ice trays or .the like, housing structure including vertically extending wall members, means for mounting said housing structure on said first coil in poor heat conduct ing relation therewith and in spaced relation-with respect to said second coil, said structure when mounted on said first coil providing a housing having openings for circulation of air therethrough, such air flowing through the housing being directed to pass in thermal exchange relation with said second coil.

2. A cooling element as set forth in claim 1 in which said mean for mounting said housing structure on said first coil is so constructed'and arranged that said housing structure is slidably movable to its mounted position.

3. A cooling element as set forth in claim I in which said means for mounting said housing structure on said first coil includes horizontally disposed rails or guides fixed to said first coil and the side walls of said housing structure are provided with spaced apart tab whichare supported on and movable along said rails.

4. In a refrigerator having a thermallyinsulated storage space, absorption refrigeration apparatus including evaporator structure" in which refrigerant fiuid evaporates in the presence of inert'gas, a housing disposed in" said space which comprises a plurality of wall sections including horizontal and vertical wall sections; said evaporator structure being disposed in the interior of said housing in good thermal relation with a horizontal Wall section adapted to support ice trays or the like, said housing being so coristructed and formed that wall sections thereof, other than said horizontal wall section in thermal relation with said evaporator structure, are in poor thermal relation with said evaporator structure so as to maintain the outer surfaces of said housing at a temperature abov the freezing temperature of moistur .prese'nt'in air in said space under stabilized temperature conditions therein, said housing having spaced apart opening providing a path of flow through the interior thereof for air in said space which is adapted to. be cooled by thermal transfer with said evaporator structure, and means includingtlie. bottom hor'i zontal'wall section of said" housing, which is in poor thermal relation with said evaporator structure, for collecting moisture formed in said housin said wall sections in poor thermal relation with said evaporator structure constituting the outer walls of said housing and whose inner faces at least in part define the path of flow for air to be cooled by said evaporator structure.

5. In a refrigerator having a thermally insulated space, absorption refrigeration apparatus including evaporator structure comprising a plurality of sections adapted to operate at different average temperature and in each of which refrigerant fiuid evaporates in the presence of inert gas, a horizontally disposed member in good thermal relation with one of said sections for supporting ice trays or the like, a housing disposed in said space which comprises horizontal and vertical wall section, and means for supporting said housing on said member so that the horizontal and vertical Wall sections thereof are in poor heat transfer relation with said one evaporator section and in spaced relation with another evaporator section, said member serving as a shelf in said housing, and said housing having spaced apart openings providing a path of flow through the interior thereof for air in the space which is adapted to be cooled by thermal transfer with said evaporator structure, said wall sections in poor thermal relation with said evaporator structure constituting the outer walls of said housing a and whose inner faces at least in part define the path of flow of air to be cooled by said evaporator structure.

6. In a refrigerator having a thermally insulated space, refrigeration apparatus including evaporator means disposed in the space, said evaporator means comprising first and second looped coils, a horizontally disposed member in good thermal relation with said first coil for supporting ice trays or the like, housing structure including vertical Wall sections, and means for supporting said housing structure on said member with said Vertical wall sections in poor thermal relation with said first coil and thermally separated from said second coil, said housing structure when mounted on said member providing a housing having spaced apart openings for circulation therethrough of air in the space, such air flowing through the housing being directed to pass in thermal transfer with said evaporator means, and said vertical wall sections in poor thermal relation with said first coil constituting the outer walls of said housing and whose inner faces at least in part define the path of flow of air through the housing.

7. In a refrigerator having a thermally insulated space, absorption refrigeration apparatus including evaporator structure providing an elongated passage in which refrigerant fluid evaporates in the presence of inert gas, a housing in said space which comprises a plurality of wall sections including horizontal wall sections, said evaporator structure being disposed in the interior of said housing in good thermal relation with a. first horizontal wall section at one level which is adapted to support ice trays or the like, and said housing being so constructed and arranged that a second or bottom horizontal wall section at a lower level is in poor thermal relation with said evaporator structure so as to maintain such bottom wall section at a temperature above the freezing temperature of moisture present in air in said space, said bottom Wall section having an opening for draining condensate collecting thereon, said housing having openings therein to provide an inlet and outlet, respectively, which are always open during normal operation of the refrigeration apparatus for circulation therethrough of air in said space, and structure including the first and second horizontal Walls to provide a passage between said inlet and outlet for cooling of air therein by said evaporator structure.

8. In a refrigerator having a thermally insulated interior, refrigeration apparatus including an evaporator disposed in said interior, said evaporator comprising a first coil operable at a low average or mean temperature for freezing purposes and a second coil operable at a higher average or mean temperature, a horizontally disposed member in good heat conducting relation with said first coil for supporting ice trays or the like, housing structure including vertical wall sections, means for mounting said housing structure on said evaporator with said vertical wall sections in poor thermal relation with said first and second coils, the thermal relation between said first coil and vertical wall sections being such that, during normal operation of the refrigeration apparatus and under stabilized temperature conditions in said interior, cooling effect produced by said first coil Will be ineffective to cause formation of frost at the exterior surfaces of said vertical Wall members when Water vapor present in air in the insulated interior condenses thereon, said housing structure when mounted on said evaporator providing a housing having openings for circulation of air therethrough, such air flowing through the housing being directed to pass in thermal exchange relation with said second coil.

WILHELM GEORG KoGEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,825,698 King Oct. 6, 1931 2,328,189 Brace et a1 Aug. 31, 1943 2,328,196 Coons et al Aug. 31, 1943 2,330,913 Philipp Oct. 5, 1943 2,363, Bixler Nov. 21, 1944 

